The letter was addressed to Mr. And Mrs. Eric Trump and was delivered to their apartment building in Manhattan. Last night, when Lara got home from work, she opened it and a puff of white powder came out. She dropped the envelope immediately, washed her hands and left the apartment. The envelope had a Massachusetts postmark.

FBI and Secret Service agents converged on the apartment. The NYPD sent in a hazmat team. According to preliminary results, the powder does not appear to be toxic.

The letter warned the Republican frontrunner to drop out of the race or his family would be harmed.

It's the second major threat to Donald Trump this week. The hacker group Anonymous has declared “total war” on the candidate.

“Now is the time to fight fascism. We have a gift for you -- Trump's Social Security number, his cell phone number and other information that could help you investigate this fascist,” they said in a statement.

The Trump campaign says the FBI is taking the threat by Anonymous seriously.

"The government and law enforcement authorities are seeking the arrest of the people responsible for attempting to illegally hack Mr. Trump's accounts and telephone information," the statement from the FBI said.